A10 3:15 vs 3:55

[Rash]

Wish I had gotten the 3.55, I’ll be upgrading. That said the 3.15 is darned fast. The pp cars get the Torsen diff, the 3.55 in the non pp cars is not the same. It’s a less expensive diff. No clue how much if any better the torsen diff is. If you plan on adding a blower or turbos stay with the 3.15

You gonna have the dealer do the upgrade or sonewhere else? You get a price quote yet? I’m considering upgrading as well.

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[Lonmon]

Now yall have me thinking about it. LOL! I am interested in what its gonna cost as well. I remember hearing that you can't just switch the gears in the 315 rear, you have to replace the whole rear. That should make it easy to install at least. I guess just finding a reasonably priced 355 rear will be the trick.

 

[drabon74]

From info rec’d here, changing the pinion and the diff in the 3.15 casing is an option, but it requires someone well versed in doing such jobs to get it done properly, not something a weekend= warrior should take on. Now this is info rec’d in several threads on mg6, no personal experience. By the time you pay someone on top of buying everything, it’s actually cheaper to buy a completed used pull off eBay and just bolt it up, should be something I could handle. Used they go for $539 shipped, I have priced them new for like $815.00. No clue what a used 3.15 goes for(would want to resell mine to offset the cost), or what’s needed to calibrate the 3.55. Also not sure if this is a used part I should avoid.

 

[Rash]

From info rec’d here, changing the pinion and the diff in the 3.15 casing is an option, but it requires someone well versed in doing such jobs to get it done properly, not something a weekend= warrior should take on. Now this is info rec’d in several threads on mg6, no personal experience. By the time you pay someone on top of buying everything, it’s actually cheaper to buy a completed used pull off eBay and just bolt it up, should be something I could handle. Used they go for $539 shipped, I have priced them new for like $815.00. No clue what a used 3.15 goes for(would want to resell mine to offset the cost), or what’s needed to calibrate the 3.55. Also not sure if this is a used part I should avoid.

Screw it , I'll just live with it. Don't feel like voiding my extended warranty by taking a chance with a used rear.

 

[DickR]

FYI the 10th gear with 3.55's is actually "shorter" (higher rpm for a given mph) than 9th gear with the 3.15's.

My GT PP A10 (3.55's) in D and normal drive mode spends most of its constant speed driving at 40 or 45 mph in 10th gear and only needs a little bit more throttle to initiate a down shift to 9th if wanted.

Here are speed in gears at 1000 rpm using 751 revs per mile oem 275/40x19 tires with the 3.55's and the 3.15's.

3.55's

4.80
7.55
10.52
12.79
14.81
17.72
22.51
26.48
33.10
35.72

3.15's

5.41
8.51
11.85
14.25
16.69
19.97
25.36
29.84
37.30
40.26

 

[Rash]

My GT PP A10 (3.55's) in D and normal drive mode spends most of its constant speed driving at 40 or 45 mph in 10th gear and only needs a little bit more throttle to initiate a down shift to 9th if wanted

What is your rpm at 43 in 10th? I use 43 because it will downshift to 9th at 42. At 43, my 3.15 A10 is at approx 1100 rpm, which seems too low to me. I bet yours is around 1400.

 

[kidamer]

but overall the difference cant be more then what 0.1 maybe 0.2 tenths in the 1/4 mi?

 

[DickR]

I have 275/35x19 tires which are 784 revs per mile. The math says 41 mph at 1200 rpm on those and 43 mph on the OEM 751 revs per mile tires . My recent post observations are with the 784 revs per mile tires but the behavior was essentially the same with the taller OEM tires. Revs per mile from TireRack specs.

 

[Lonmon]

Someone with the 355 had said they are at 72mph at 2000 rpm in 10th. I am at 80mph at 2000 rpm in 10th with the 315 FYI. I kinda expected the difference to be less but I guess that sounds about right.

 

[DickR]

Someone with the 355 had said they are at 72mph at 2000 rpm in 10th. I am at 80mph at 2000 rpm in 10th with the 315 FYI. I kinda expected the difference to be less but I guess that sounds about right.

Correct per the data I posted above. 3.55 is about 35 mph per 1000 rpm and 3.15 is about 40 mph per 1000 rpm in 10th.

 

[BmacIL]

If you do a lot of highway driving: 3.15. Otherwise, 3.55 since no shifting involved in those 10 gears.

 

[MX Raptor]

If you do a lot of highway driving: 3.15. Otherwise, 3.55 since no shifting involved in those 10 gears.

Yeah I live in the city, so it’s continuously stop and go. And if it is a tenth or two difference between the 3:15 and 3:55 in the 1/4. I’ll go with the faster of the two.

Is there anyone on here that is close to each other, that have the same modifications (if any) but one with a 3:15 and the other a 3:55 and record a “scientific test” between the two, to see the difference in acceleration?

 

[kidamer]

Yeah I live in the city, so it’s continuously stop and go. And if it is a tenth or two difference between the 3:15 and 3:55 in the 1/4. I’ll go with the faster of the two.

Is there anyone on here that is close to each other, that have the same modifications (if any) but one with a 3:15 and the other a 3:55 and record a “scientific test” between the two, to see the difference in acceleration?

Yes I was at the track last night, Why I posted earlier I should have said that, the 3.55 and 3.15 were within 0.1 with each other. of the 3 races I saw between them the 3.15 non pp went 12.17 and the 3.55 pp went 12.02. and the other times were almost spot on within in the same differences in time

 

[wireeater]

I test drove the A10 months ago with the 3.15 and wasn't mesmerized by the low end but I liked the shifts. Last weekend I drove the PP with the 3.55 and it felt like a completely different car which made me want it right there, so I got it. It rips so hard off the line that I am never prepared for it.

 

[Grintch]

If I had to do it again, I'd go with 3.55. I feel like the RPM are too low in tenth gear when doing 40-45 mph in D mode - it feels sluggish in that situation, and can lug when trying to accelerate. Yes, you could manually upshift, or just use S mode, but I don't want to HAVE to do anything. It seems like those with 3.55 don't notice the issue as much if at all since RPMs are a bit higher. See this thread: https://www.mustang6g.com/forums/showthread.php?t=102341

So it has you in 10th gear at 40 mph? That's terrible, does putting it in Sport mode make it not rush to shift up as much?

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